 /*******************************************************************************
  * Copyright (c) 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.contexts;

 import org.eclipse.core.expressions.IEvaluationContext;
 import org.eclipse.ui.internal.services.IEvaluationResultCache;

 /**
  * <p>
  * A token representing the activation of a context. This token can later be
  * used to cancel that activation. Without this token, then context will only
  * become inactive if the component in which the context was activated is
  * destroyed.
  * </p>
  * <p>
  * This interface is not intended to be implemented or extended by clients.
  * </p>
  *
  * @since 3.1
  * @see org.eclipse.ui.ISources
  * @see org.eclipse.ui.ISourceProvider
  */
 public interface IContextActivation extends IEvaluationResultCache {

     /**
      * Clears the cached computation of the <code>isActive</code> method, if
      * any. This method is only intended for internal use. It provides a
      * mechanism by which <code>ISourceProvider</code> events can invalidate
      * state on a <code>IContextActivation</code> instance.
      *
      * @deprecated Use {@link IEvaluationResultCache#clearResult()} instead.
      */
     public void clearActive();

     /**
      * Returns the identifier of the context that is being activated.
      *
      * @return The context identifier; never <code>null</code>.
      */
     public String getContextId();

     /**
      * Returns the context service from which this activation was requested.
      * This is used to ensure that an activation can only be retracted from the
      * same service which issued it.
      *
      * @return The context service; never <code>null</code>.
      */
     public IContextService getContextService();

     /**
      * Returns whether this context activation is currently active -- given the
      * current state of the workbench. This method should cache its computation.
      * The cache will be cleared by a call to <code>clearActive</code>.
      *
      * @param context
      * The context in which this state should be evaluated; must not
      * be <code>null</code>.
      * @return <code>true</code> if the activation is currently active;
      * <code>false</code> otherwise.
      * @deprecated Use
      * {@link IEvaluationResultCache#evaluate(IEvaluationContext)}
      * instead.
      */
     public boolean isActive(IEvaluationContext context);
 }

